The overall purpose of this proposal is to explore how the speech production system responds to the sensory information provided by multichannel cochlear implants in post-lingually deafened adults. The specific aims of the proposal are to: a) examine if relatively rapid changes in vowel formant frequencies occur when implants are turned off versus on; b) determine, if changes in formant frequencies occur whether these changes are related to the type of sensory information provided by the implant; c) investigate if the speech changes are perceptually relevant to listeners; d) explore if the changes in speech are related to onset or length of deafness; and e) evaluate the types of articulatory adjustments made when the implant is turned off versus on using the University of Wisconsin's X-ray Microbeam Facility. Measurements will be compared within individual subjects, across the prosthetically aided versus nonaided conditions using ANOVAs. Dependent variables will be first and second formant frequencies and pellet locations. Newman-Kuehls range tests and trend analyses will be used to examine possible trial effects. Correlational analyses will be used to examine relationships between onset and length of deafness to our dependent variables. Comparing values obtained when the device is turned on versus off will allow us to determine if rapid speech changes occur in the presence of no auditory feedback. Manipulations of the type of information provided by the implant will allow us to compare speech produced under auditory, spectral versus auditory, nonspectral feedback conditions. Tracking the changes in jaw, lip, and tongue positions when the implant is turned off versus on will allow us to examine the articulatory strategies used by speakers when auditory information is available. Data from these studies will enable us to explore how auditory feedback is used in speech production and may provide information useful for designing remediation programs for individuals experiencing post-lingual deafness.